Forza 6 DLC questions/list of DLC

So Forza 6 is out today, my copy came in from BB's GCU.

I went onto eBay to view what "exclusive" DLC is out there. Can anyone help with the list of retailers? I am trying to figure out how to get them all, but at a good price. If I know where the DLC came from, and how "rare" it is, it might help me negotiate with sellers.

10 Year Anniv Pack - Included with Day 1 edition

BMW M4 Coupe - Best Buy

WRX STi - Gamestop

Furious 7 (Dom's Charger) - Microsoft, when you buy Furious 7

http://www.xbox.com/en-US/video/fast-and-the-furious-7-dlc-offer

Challenger (Battletoads edition) - ????

Audi TTS - ????

Does anyone know where the Battletoads edition and TTS came from? (I've found them on eBay)

What else is out there that I am missing? If anyone gets a Furious 7 car and wants to sell, hit me up! ​

The battletoads challenger was from gamestop.

Bestbuy will have the season pass on sale tomorrow

I'm selling my 10th Ann. code and my BMW from Best Buy, most likely on eBay let me know if you might be interested in case I don't get any bids or the auctions fall through.